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Etna update, 9 April 2011

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Strombolian activity and initiation of a small lava overflow from the pit crater on the east flank of the Southeast Crater cone at 18:00 GMT on 9 April 2011. The conspicuous gas plume drifting over the Southeast Crater cone is released by the Northeast Crater, which in this perspective lies behind the cone. Photo taken from Trecastagni by Boris Behncke, INGV-CT

Since the morning of 8 April 2011 a new phase of eruptive activity is under way at the pit crater that lies on the eastern flank of the Southeast Crater cone.

This resumption of eruptive activity has been preceded by a series of gas and ash emissions, rarely with minor quantities of incandescent material, during the period from 29 March through the first few days of April.

 
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Strombolian activity within the pit crater photographed on the late morning of 8 April 2011 from the eastern crater rim by Boris Behncke, INGV-CT

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Strombolian activity and emission of intracrater lava flow (steaming area at right) on the afternoon of 9 April 2011. Photo taken by Mauro Coltelli, INGV-CT

Throughout the day of 8 April, the eruptive activity showed low levels of intensity, and was characterized by small Strombolian explosions that occurred from two vents located in the western portion of the crater floor. Ejecta produced by this activity were entirely confined to the interior of the crater depression.

During the morning of 9 April 2011, the INGV-Catania seismic network recorded a slight increase in the seismic activity produced by the Strombolian activity, which gradually grew in intensity.

From the early hours of the afternoon, concomitantly with the augmentation in the explosive activity from two intracrater vents, lava was emitted at a sustained but low rate, rapidly covering the crater floor.

At sunset, the first blocks of incandescent lava appeared within the breach in the eastern rim of the crater, heralding a small overflow of lava shortly before 18:00 GMT. The lava slowly advanced from the base of the Southeast Crater cone toward the western headwall of the Valle del Bove.

On the late evening, the lava flow continued to be fed, and had reached a length of about 1 km; at the same time frequent but small Strombolian explosions continued within the crater, which rarely threw incandescent ejecta beyond the crater rim. The gradual increase in the volcanic tremor amplitude continued, and the source of the tremor had shifted from its previous position below the Northeast Crater toward the active vent, as it had done also during the eruptive episodes of 2-3 and 12-24 January and 18 February.

At midnight, the Strombolian activity remained relatively weak, while the lava flow continued its slow advance toward the Valle del Bove.

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Strombolian activity and lava flow at 20:00 GMT on 9 April 2011, photographed from Piano del Vescovo (southeastern flank of Etna) by Boris Behncke, INGV-CT

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